1. Field of the Invention
The present invention relates to an image displaying apparatus, and more particularly to an image displaying apparatus which is so arranged that a compact optical system having image information (display information), such as a liquid crystal device, is set on the head or in front of the face of an observer whereby the observer can observe the image information as an enlarged virtual image with a wide angle of view.
2. Related Background Art
There are large-scale CRT display apparatus, projection TV apparatus, etc. conventionally used as image displaying apparatus arranged to enable image information displayed on an image display device such as a liquid crystal device to be observed as a picture on a large image plane with presence.
These image displaying apparatus had some problems: they need a large space; a suitable observation distance cannot be secured when installed in a narrow room; it is impossible for individuals to respectively watch different programs; etc.
As an example to solve the problems, Japanese Laid-open Patent Application No. 3-203478 describes an image displaying apparatus, as shown in FIG. 1, which uses an optical system set near the face of an observer to guide a beam from an image display device directly to the eye (observer's pupil) whereby the observer can observe the image information on a large image plane.
Describing the major part of the drawing, 221R, 221L denote liquid crystal color televisions for right eye and for left eye, respectively. Image information displayed on each liquid crystal color television 221R, 221L is reflected by a trapezoid beam splitter (half mirror) 222R (222L, not shown) set in front of either of the eyes, so that part of reflected beams impinge on a concave mirror 223 set ahead. Beams reflected by the concave mirror 223 pass through the beam splitter 222R (222L) to enter the eyes of an observer (not shown).
Then the observer observes the image information displayed on the liquid crystal color televisions 221R, 221L as virtual images at a predetermined position ahead of the concave mirror 223.
Also, the above image displaying apparatus can permit the observer to observe a stereoscopic image while displaying display information with binocular parallax between the right eye and the left eye of observer.
Further, Japanese Laid-open Patent Application No. 4-221920 describes an image displaying apparatus in which a convex lens enlarges a picture displayed on a polarized-light controlling display and in which polarization separating means set in front of the observer's pupil guides the polarized picture into the observer's pupil, whereby an enlarged virtual image can be displayed as superimposed over the external view.
In the conventional image displaying apparatus all the color televisions and the polarized-light controlling displays used as displaying devices were transmission type liquid crystal devices illuminated with backlight.
The liquid crystal devices, for example TFT liquid crystal color televisions, have low aperture rates of about 40% in the cases of liquid crystal panels of currently available products, thus failing to obtain a sufficient transmittance. Then, in order to achieve sufficient display luminance, it was necessary, for example, to increase an intensity of backlight or to provide a sheet multi-lens array on the aperture portion, which was a hindrance to decreasing the size and the weight of the entire apparatus. It was also difficult to decrease the dissipation power because of the need of the high-power backlight.
There are various factors for decreasing the aperture rate of liquid crystal device. For example, main factors are TFT, wiring, auxiliary capacitance, and a portion of black matrix on a color filter covering gaps between them. Then an improvement in aperture rate has been tried for example by decreasing the dimensions of TFT or wiring, decreasing the area of auxiliary capacitance, etc.
However, these methods had the limits due to restrictions in the semiconductor process technology such as the TFT process, which was a problem.
Further, because the conventional image displaying apparatus were so arranged that a liquid crystal panel was observed after enlarged by a lens or a concave mirror, pixels were observed as being very rough. Thus, display quality was insufficient.
To solve this problem, there is a method to increase the density of pixels in the liquid crystal panel. This method, however, had a problem that an increase in density resulted in an increase in number of such elements as TFT and wiring, which lowered the aperture rate.
In addition, a transmission type liquid crystal television needed two polarizing plates arranged in a state of crossed Nicols, which was also a factor to lower the display luminance.